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' Beacon Station No 641 December 8, 1997 Stockton, all Additional Subsurface lnve ti a i Re-rt Soil Vapor t i n Well In "11n - Phase VE-5, VE-6, VE-7, and VE-8 are each 2-inch ID, schedule 40 PVC soil vapor wells constructed in 10-inch diameter soil borings drilled to 55 feet bsg Wells VE-5 and VE-6 were installed as a dual completion in the 10-inch diameter soil boring VE-5 Wells VE-7 and VE-8 were installed as a dual completion in the 10-inch diameter soil boring VE-7 The ' screened intervals are VE-5 = 40 to 50 feet bsg, VE-6 = 22 to 32 feet bsg, VE-7 = 40 to 55 feet bsg, and VE-8 = 22 to 32 feet bsg Blank PVC well casing was installed from the top of each screened interval to the surface The annular space opposite each well screen was backfilled with # 3 Monterey sand, and a seal of bentonite was placed in the intervals 1 between the top of the filter sand and the bottom of the screened interval of the next nested well A bentonite seal was also placed in the interval from the bottom of the screened interval of well VE-5 to the total boring depth (50 to 55 feet) These bentonite seals vaned from 4 to 7-feet thick, as indicated on the boring logs A neat cement bentonite grout was used to complete the annular seal from the top of the uppermost seal to approximately one foot bsg A PVC cap was placed on the top of each vapor well until the wells are plumbed into a soil vapor extraction system The top of each well cluster was sealed within a 24-inch diameter, water-tight, steel traffic-rated box previously installed over 18-inch PVC conductor casings The construction details are shown on the corresponding boring logs in Appendix C t512argeW n i 2 SW-1 , a 2-inch ID sparge well, was constructed in the 8-inch diameter soil boring SW-1 The well was completed with 5 feet of schedule 40 PVC well screen with 0 020-inch factory-machined slots The bottom of the screened interval, also the total drilled depth of the soil boring, was approximately 65 feet bsg Blank PVC well casing was installed from the top of the screened interval at approximately 60 feet bsg to the surface The annular space opposite the well screen was backfilled with # 3 Monterey sand to approximately one foot above the screened interval A four-foot seal of bentonite was then placed above the filter sand and hydrated with approximately ten gallons of fresh water A neat 1641-13t � 7 HORIZON ENVIRONMENTAL INC